Other forms: public sectors
When economists talk about the public sector, they're referring to everything that's run by the government, like public schools, libraries, and the military.
In economics, things are generally divided into the public sector and the private sector, which is composed of for-profit companies that are privately owned. Services for the public, like hospitals, street lamps in parks, and road crews that clear snow off the highway, are all part of the public sector. First used in the 1930s to mean "a section of the economy," sector is derived from the Latin secare, "to cut or divide."